This note by the KECCAK Team refers to Table 1 of "A SAT-based preimage analysis of reduced KECCAK hash functions" by Pawel Morawiecki and Marian Srebrny. "On the Core 2 Duo, the best implementation of Keccak-f[1600] takes about 1600 cycles for 24 rounds. As an alternate way to present the time needed to solve the SAT problem, you could express this time using one evaluation of Keccak-f as unit. E.g., in the first line of the table. Keccak-f[1600, nr=3] takes about 200 cycles. With 2GHz, a time unit is therefore 200/(2*10^9)=10^-7 second. So 1 second of CPU time is about 10^7≈2^23.25 evaluations of Keccak-f[1600, nr=3], which must be compared to 2^24 in the exhaustive search. The third line is more interesting: 1852 seconds is about 2^34.11 evaluations, which must be compared to 2^40."